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Boatwright, J.L., 1979

The nature of the earthquake focus as inferred from body-wave observations

Bibliographic Reference

Boatwright, J.L., 1979, The nature of the earthquake focus as inferred from body-wave observations: New York City, New York, Columbia University, Ph.D. dissertation, 215 p.


A class of kinematic rupture models is constructed to approximate numerical and analytical solutions to the dynamic problem of shear fracture. These models incorporate self-similar rupture growth, a range of stopping behavior and causal healing, which propagates into the interior of the rupture areas at the compressional wave velocity. The far-field body-waves radiated by these models are analyzed to determine simple techniques for estimated source dimension and dynamic stress drop. The effects of rupture velocity and rupture geometry on the directivity of the body-wave pulse shapes are also investigated. These results are applied to the analysis of two high stress drop earthquakes which occurred beneath the Shumagin Islands, Alaska, and of a multiply recorded aftershock of the 1975 Oroville, California earthquake. The stopping phases radiated by the Oroville aftershock are analyzed in order to investigate the unmodelled complexity of the rupture. The combination of the results from these two techniques provides the most detailed description of rupture ever obtained for a moderate-sized earthquake.

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